Piezoelectric properties of lead-free (Na_(0.5)Bi_(0.5))TiO_3-(Na_(0.5)K_(0.5))NbO_3-BaTiO_3 ceramics

摘要

The microstructural evolution and piezoelectric properties of lead-free ceramics (0.98-x)(Na_(0.5)Bi_(0.5))TiO_3-x(Na_(0.5)K_(0.5))NbO_3-0.02BaTiO_3 (0 ≤ x ≤ 0.98, abbreviated as (0.98-x)NBT-xNKN-0.02BT) were investigated. The effects of the amount of NKN on the crystal structure, microstructural evolution, and piezoelectric properties were examined. The 0.93NBT-0.05NKN-0.02BT ceramics having a lower NKN content gave good performances with piezoelectric properties of d_(33) = 140 pC/N and k_p = 21%, because of the soft additive Nb~(5+) ions at the B sites. However, a paraelectric cubic phase was observed in the wide range of compositions between x = 0.1 and x = 0.9. At a higher NKN content of x > 0.9, a morphotropic phase boundary (MPB) between the tetragonal and orthorhombic phases was found in the 0.015NBT-0.965NKN-0.02BT ceramics, and the piezoelectric properties were enhanced (d_(33) = 135 pC/N, k_p = 29%). The piezoelectric properties of this system were closely related to its crystal structure.